ISC Moderation Relay Timings

A typical turnaround time is about 15 seconds, from time of injection to time of receipt.
Certain spam filtration measures on each end can artificially extend the apparent
transit time.

Yellow lines denote instances where injection of the probe was declined
by the particular relay. Such cases are "soft" SMTP failures, and had the probe been
a real article submission, would simply result in the transmitting news server trying again
at a different relay a few minutes later. For example, the many failures on ucsd.edu mailservers
indicate either excessive load (deferring to another host) or greylisting.

Red lines indicate probes that were accepted by the moderation relay, but never reached
the collection point. Had those been real submissions, the article would have been lost.
Fortunately, given the emphasis of the SMTP standard on reliable delivery and queue-and-retry
delivery mechanisms, this is a very rare event (always denoting a software bug or
misconfiguration, generally attended-to swiftly.)